1. Field of the Invention
The present invention relates to a power transmitting apparatus that is mounted on a hybrid vehicle including plural drive sources having different power generation principles.
2. Description of Related Art
A hybrid vehicle is a vehicle including plural drive sources having different power generation principles, such as an engine for converting thermal energy into kinetic energy to generate dynamic power and a rotary machine having an energy regeneration function, as drive sources for traveling. The hybrid vehicle is a vehicle including an internal combustion engine such as a gasoline engine or a diesel engine and a rotary machine such as an electric motor having a power generation function or a hydraulic motor having a pressure accumulating function as drive sources. In addition, the hybrid vehicle is a vehicle that can improve energy efficiency and reduce an amount of exhaust gas by effectively using characteristics of the engine and the rotary machine. An example of such a hybrid vehicle is described in Japanese Patent Application Publication No. 2008-120234 (JP 2008-120234 A).
A hybrid drive device described in JP 2008-120234 A includes an engine, a first motor having a function of generating electric power with the dynamic power of the engine, and a second motor outputting dynamic power to an output member with the electric power generated by the first motor as drive sources. The first motor and the second motor are arranged on the same axis and a power split mechanism that splits the dynamic power output from the engine to the first motor side and the output member side is disposed between the first motor and the second motor. In the hybrid drive device described in JP 2008-120234 A, a transmission gear device changes a rotation speed of the engine and transmits a torque to the power split mechanism. The transmission gear device is disposed between the first motor and the second motor.
Japanese Patent Application Publication No. 2008-265598 (JP 2008-265598 A) describes a hybrid vehicle having a power split mechanism that includes an engine, a first motor, a second motor, and a planetary gear unit having three rotation elements. The hybrid vehicle described in JP 2008-265598 A further includes a clutch that fixes the output shaft of the engine so as not to be rotatable. The first motor is connected to the output shaft of the engine via the power split mechanism and the second motor is connected to driving wheels. The operations of the engine, the first motor, the second motor, and the clutch are controlled on the basis of a driving force required for the vehicle. The hybrid vehicle is configured to perform motor-driven traveling in which both the first motor and the second motor are driven in a state where the power split mechanism is made to serve as a deceleration mechanism or an acceleration mechanism by engaging the clutch to fix the output shaft of the engine.
Japanese Patent Application Publication No. 2008-265600 (JP 2008-265600 A) describes the same configuration as the hybrid vehicle described in JP 2008-265598 A. JP 2008-265600 A describes that the operation of the engine is stopped and the rotation of the two motors are controlled using a map in which torque split for most efficiently driving the two motors is defined on the basis of an accelerator operation amount, a vehicle speed, and a gear ratio of a transmission when a condition in which the clutch is engaged to fix the crank shaft of the engine so as not to be rotatable is established.
The hybrid drive device described in JP 2008-120234 has a configuration in which a transmission gear mechanism for changing the rotation speed of the engine is added to the configuration of the power transmitting apparatus for a hybrid vehicle in the related art including the engine, the electric motor, and the power split mechanism. By employing this configuration, it is possible to operate the engine at a rotation speed more advantageous in fuel efficiency depending on a required driving force or a traveling state. Accordingly, it is possible to improve the energy efficiency of the hybrid vehicle.
On the other hand, the transmission gear mechanism includes a gear mechanism and a clutch or a brake for controlling the transmission. Accordingly, compared with a power transmitting apparatus for a hybrid vehicle in the related art not having such a transmission gear mechanism, the number of components increases or the number of assembly steps increases to correspond to the addition of the transmission gear mechanism. As a result, the assembly of the apparatus may be complicated and the productivity thereof may be lowered.